$\dfrac{2}{5} \div \dfrac{1}{7} = {?}$
Explanation: Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. The reciprocal of $\dfrac{1}{7}$ is $\dfrac{7}{1}$. Therefore: $ \dfrac{2}{5} \div \dfrac{1}{7} = \dfrac{2}{5} \times \dfrac{7}{1} $ $ \phantom{\dfrac{2}{5} \times \dfrac{7}{1}} = \dfrac{2 \times 7}{5 \times 1} $ $ \phantom{\dfrac{2}{5} \times \dfrac{7}{1}} = \dfrac{14}{5} $